Refrigerant evaporator



R. W. WATERFILL.

I REFRIGERANT EVAPORATOR 4 Sheets-Sheet 1 Filed Sept. V30, 1938.INVENTOR ROBERT W WATER/ILL BY @rm, 'Q WY- ATTORNEYS Patented June 24,194i Robert W. WatcrlilllMontclair, N. 3:, assignor to Bucnsod- StaceyAir Conditioning, Incorporated; New York, N. Y., a corporation orDelaware Application September 30, I938, Serial No. 232,581

ber of thin vertical channels through which i 18 Claims.

This invention relates to improvements in refrigerant evaporators, andmore particularly to a method and means for distributing refrigerantliquid over the heat-exchanging surfaces of a shell-and-tube evaporator.

The principal object of the invention is to provide an evaporator orcooler into which liquid refrigerant may be introduced directly from thev condenser, and its own energy utilized to raise the liquid from thebase of the evaporator-and circulate it over the heat-exchangingsurfaces therein.

It is another object of the invention to provide a shell-and-tube coolerwith a plurality of narrow channels extending vertically from the baseof the shell upwardly between the tubes of the bani: which serve toconfine flash gas resulting from the evaporation of liquid refrigerantintroducedinto the base of the shell to cause it to lift unevaporatedref a v: i through the channels and over the heat-e l surfaces of thetubes,

-It isv yet another obiect of the invention to slightly above the baseof the shell to provide passageways between adjacent sections whichprovide a' shell-and-tuberefrlgerant evaporator characterized in thatthe'tube. bank'is divided longitudinally into a plurality of sectionshavin their open upper'ends in free communication and their open lowerendssealed'one from another by the presence of liquidi-refrigerant in isfurther divided into a. plurality rot vertical liquid refrigerantintroduced into the base of theshell may percolateupwardly over theheatexchanging surfaces of the tube bank in ac cordance with theforegoing objects.

It is yet another specific object of the invention'to provide anevaporator of the character described having a pair of verticallydisposed plates dividing the tube bank longitudinally into threesections with their lower edges spaced .may be sealed by the presence ofrefrigerant liquid in the base of the shell, and a conduit fordischarging jets of liquid refrigerant from the condenser side of thesystem into the base of the shell immediately beneath the center sectionof the tube bank so that flash gas resulting from the evaporation ofsome of the introduced liquid will be confined within vertical channelsformed between the lust-mentioned vertical plates and a plurality ofplate fins extending crosswise of the tubeslof the center section tocause it. to lift remaining liquid therethrough and to discharge it overthe tubes in the two outer. sections of the bank.

7 The foregoing and other objects of the invena for economy inmanufacture and efficiency in channels through which refrigerant liquidmay percolate upwardly from the-base oi the'shell over the surfaces ofthe tubesin that section and be discharged into an adjacent section fromwhence it may flow downwardly over the tubes therein and return throughthe liquid seal to that portion ofthe base of the shell immediatelybeneath the vertical channels in the first-mam tioned section. a g It isa further object of the invention to discharge a plurality of streams ofliquid refriger ant from the condenser of the refrigerating system intothe shell of the evaporator immediately beneath the vertical channelsmentioned in the foregoing objects for the purpose of inducing a flow ofliquid into such channels, and to provide an initial volume of flash gaswhich is needed, or at least is highly desirable, in starting thecirculating cycle.

It is a more specific object of the invention to provide ashell-and-tube evaporator with a. pinvoperation, will be more apparentfrom the follow'lng'dmription when read in connection with theaccompanying drawings, in which Figure 1 is a perspective fview, partlyin sec- -tion,of a fragment of a shell-and-tube evaporator embodying theprinciples of the present invention and illustrating in "a more or lessdia rainmatic fashion the manner in which it operates: v

Fig. 2 is an end elevational view of an evaporator embodying theinvention in practical form; i v

Fig. 3 is a longitudinal section taken on the line 3-3 of Fig. 2;

Fig. 4 is a vertical section taken on the line 4-6 of Fig. 3;

Fig. 4a is a plan view of a fragment of the tube bank of Fig. 4;

Fig. 5 is an elevational' view of a fragment of the tube bank of theevaporator illustrated in Figs. 2, 3 and 4, with certain parts thereofbroiken away better to show the underlying ones; an

Fig. 6 is an end elevational view, in section and on an enlarged scale,of a fragment of the evaporator-of Figs. 2, 3 and 4 and illustratingavailable to lift less and less shell.

fined within the center section 0, and can escape best results, maximumheat transfer, the surfaces of the tube bank should be maintained in awetted state. In conventional present-day systems this is done either byproviding a circulating pump which draws a constant volume of liquidfrom the base of the shell and showers it over the bank of tubes, orby-the submergence of the bank in a large volume of refrigerant, all ina well understood manner. The evaporator of the present invention,however, needs no such pump. It is arranged to utilize the energy ofrefrigerant introduced into the shell from the condenser, as representedby the pressure differential between the condenser and evaporator, aswell as the energy released by the change of state of some of therefrigerant from a liquid to a gas, to lift remaining liquid from thebase of the shell and to distribute it over the heat exchanging surfacesof the tube bank. Briefly stated, this is done by discharging jets ofrefrigerant from 'the condenser of the system within the base of theshell immediately beneath the tube bank, and by confining flash gasresulting from the evaporation of some of the refrigerant to cause it tofroth the remaining liquid, and to only through the open upper ends ofthe channels M. In so doing it bubbles through the liquid in the lowerends of the channels, and creates a light froth of liquid and gas, whichnecessarily is lifted through the channels under the influence of theescaping gas 'as well as by the action of the jets of introduced liquid.This column of froth, obviously, 'serves to maintain the surfaces of thefins and tubes of the center section thoroughly. wetted.

The volume of confined flash gas is augmented as the action proceeds bythe evaporation of liquid from the surfaces of the tubes through heatinterchange with the mediumtherein. This additional gas,'of course,provides additional energy to lift the froth and discharge it from thelift the froth through a plurality of vertical channels over the heatexchanging surfaces of the tube bank. Once the action starts, and theflash gas and provides additional energy to assist in conveying thefroth to the .top of the bank.

. It is evident that the action" accumulates as it proceeds, i. e., moreand more energy is made liquid-as the froth rises through the bank.

The foregoing maybetter be understood by considering the operation of apractical embodiment of the invention. For thispurpose reference will behad to the more or less diagrammatic upper ends of the channels. A tthatpoint, i. e., thetop of thechannels are defined by the upper edgesof the dividing plates 96, {he macaw rapidly expands, breaks up thefroth, and throws the remaining liquid in all directions. Some of itpasses upwardly to wet the tubes of the center section lying above theupper ends of the channels, and some of it is blown sidewise into theadjacent side sections S. The latter drips downwardly over the fins andtubes-in those sections to keep their surfaces thoroughly wet'ted. Someof it is necessarily evaporated by heafigii ten change with the mediumto be cooled. The resulting vapor, however, is not confined, but mayreadily escape into the upper portion H of the shell without interferingwith the downward flow of liquid over the heat exchanging surfaces.There it Joins other vapor to be withdrawn from the shell by acompressor or absorber (not shown) in a well unders'toodmanner.

Any excess liquid drains from the fins and tubes and collects in thebase of the shell be- 40 neath the side sections S of the tube bank fromrepresentation-of the invention in Fig. 1. There liquid refrigerant isintroduced into the shell H of the evaporator from a condenser (not Ishown) through the orifices l2 in conduit l3 located in the base of theshell immediately be-.

neath the center section 0 of, the tube bank. This introduced liquid,being under greater pressure than that existing in the evaporator, isdischarged upwardly in the form of jets and entrains some of the liquidfrom the base of the shell and carries it into the lower ends of thewhence it must be returned to the center section in order that thecirculation may continue. In the preferred embodiment the return isprovided for in a very simple way, namely, through liquid sealedpassageways connecting the bases of adjacent sections of the tube bank.Thus, and

' again referring to Fig. l, it-will be noted that the dividing platesl6 extend down into the reservoir of liquid in the base of the shell,but have their lower edges spacedfrom the surface of the shell to definesmall passageways between the center and the two side sections. Theoperation is-simple and wholly automatic; As scenes the refrigeratingsystem is started, the pools of liquid H3 in the side sections promptlybuild up to points. at which their static heads just balance the columnsof froth in the channels M of the center section. Thereafter, any excessliquid draining into these pools merely displaces liquid therein causingit to pass under the lower edges of the dividing plates it andinto thecenter section 0:

The constructional details of a preferred practical embodiment oftheinvention are illustrated, in Figs. 2 to 6 inclusive. In thatembodiment the main body of the shell H is formed from a section ofcylindrical, steel tubing 20, which is supported on'legs 2i welded toits outer surfaces 24.- The purpose of these last-lnentioned parts,which may hereinafter be referred to as the base and sides of the shell,is to reduce the effective volume of the base portion of the shell tothat actually required, andthus to reduce the quantity of refrigerantwhich must be placed in the system. Appropriate breather pipes 25 (Figs.3 and 4) connect the used and. unused spaces to equalize the pressure inall parts of the actual shell.

The tube bank 10 (Fig 4) is built up from two units 26 and 21 in orderto facilitate assembly of the many tubes and fins, and for other reaaremounted in an appropriate rack with their various tube openings properlyaligned. Individual tubes 28 may then be threaded through the alignedopenings and, by the application of hydraulic pressure, may be expandedso as to engage each plate, thus to secure the various parts inassembled relation. It will be noted in Fig. 6 that each fin has acentral slitfor the reception of the dividing plate It which may beinserted at this or a prior time as may be most convenient. At its loweredge the dividing plate joins the metal sheet 32 disposed across thebottom of the sub-unit 29 for its full length, and the bottom in turnjoins th sheet 33 extending along the side of the sub-unit to a pointsubstantially opposite the break in the filler plate 2d. The unit iscompleted by the application at appropriate times of the inner sideplate 35-, the framework 38, and (Figs. 3 and 5) the return bends 3'! tothe opposite ends of the individual tubes 28. The open end portions 38of the interconnected tubes then all lie at one end of the unit forready connection to the upper header 39, the two center headers M1, andthe lower header 4 l.

The other main unit 21 is substantially ldenscribed, except insofar asits sub-units 29 and a 30 are reversed right for left. The-two units mayhe slid into place-in the main body of the shell along the rails 42 and43 attached to the center and side edges of the deck plate 23. When inposition, the cap M may be bolted to the flange d5 of the shell, and theheaders 39, 40 and M of the units connected to the inlet and outletconnections 46 and M. In assembled relation the two outer subunits 29then serve as the outer sections S of the complete bank III, while theadjacent sub-units 30 serve conjointly as is brought in through the sideof the shell and carried beneath thedeck plate 23 where it is dividedinto two branches Ma and lilb, one extending under each of thesub-sections 3D. In this particular embodiment it is to be noted thatthe deck serves as the actual top of each of the branches of theconduit, and is pierced at regularly spaced intervals to provideorifices l2 corresponding to those Fi .1. r Other constructional detailsof the evaporator will be considered in the description of the operationof the system.

The operation of the evaporator of Figs. 2 to 6 as a part of a completerefrigerating system is functionally identical with that described inconnection with Fig. 1.

Figs. 3, 4 and 6, liquid refrigerant introduced Thus, and referring nowto from the condenser of the system throughthe two branches ofconduitI3, is discharged upwardly through the orifices l2 into thetwosubsections 30, and into the-lower open ends of the channels M definedbetween the 'fins l5, the dividing plates l6, and the side plates35.Some of that liquid immediately evaporates. The resulting flash gas isconfined, however, in the channels M, and can escape only through theirupper ends. In so doing it forms froth and lifts that froth through thechannels to maintain the fins .and tubes of the center sectionsthoroughly wetted. At the top of the channels, and just as previouslydescribed, the flash gas breaks up the froth and throws any remainingliquid in all directions, some of it passing upwards over the adjacenttubes in the center sub-units 3!), and the remainder being blownsidewise over the tubes in the upper portions of the sub-units 29 FromAny excess, of course, collects in the bottoms of the troughs withinwhich the tubes of the outersections lie. When a suificient pool hasbeen built up excess liquid then drains through the openings 48 in theouter side plate '33, and passes down between the side plate 33 and theadjacent surface of the filler 24, under the rails t3 which it may benoted (Figs. 3 and 6) are supported above the deck 23 on spacers t9, andthrough the passageway 50 beneath the bottom 32back into the base of thesub-section 3!]. There it meets the incoming streams of liquid,introduced at condenser pressure through the orifices l2, and is carriedinto the lower ends of the vertical channels 15 of the sub-section 30again to percolate upwardly with the escaping flash gas to repeat thecycle just described.

In this form of the invention it will be noted that the lower tubes ofeach sub-unit 29 lie wholly within a trough defined by the dividingplate Hi, the bottom plate 32, the side plate 33 and the two end supportplates 34. The bases of these sub-units 29 are effectively separatedfrom those of sub-units 30 by the presence of liquid in the spacebetween the bottom 32 and the deck plate 23 and that between the side 33and the adjacent surface of filler 24. passages are dry when theevaporator is first started, liquid entering through the orifices l2escapes through them and promptly builds up a static head between theside plate 33 and the adjacentsurface of the filler, spilling into thetrough through the openings 48 if necessary, sufficient to balance thehead in the sub-units 30 so that the percolating action may proceed. Itwill readily be recognized by those skilled in the art that the presenceof the deck plate 23 and the filler 24 reduces the efiective volume ofthe shell to that which is actually required and thus reduces thequantityof refrigerant necessary for proper operation to a minimum.

in the conduit 13 of- If these The large majority of the portions of thefins l5 within the sub-units 30 have their lower edges spaced slightlyabove the surface of the deck plate 23. An occasional one of them lEa,at regularly spaced intervals, extends below the others, and has itslower edge resting on the deck plate, as may best be seen in Fig. 5.These extended fins l5a serve to.clivide the space immediately beneaththe sub-units 30 into a number of longitudinal compartments into each ofwhich liquid is discharged from one or more of the orifices l2. This isdone for the purpose of securing better distribution of the liquidthroughout the entire sub-section 3G'to prevent any tendency of theliquid ,to flow into any particular part of the sub-section 30 and leavethe remainder more or less dry.

The refrigerant fiash gas or vapor escapes the tube bank is divided intoseveral longitddinal sections by the presence of the plates I6; andprovision has been made for introducing liquid refrigerant into theevaporator shell immediately beneath one of these sections. This hasbeen done in order to confine the initial volume of.

flash gas available from the liquid within a relatively small spacewhere it may function most,

"efiectively as a priming agent to start the perfrom the upper part ofthe tube bank at fairly high velocity. As always, there is some tendencyon the part of this escaping gas to entrain and carry liquid with it. Aneliminator it is therefore positioned immediately above the tube bank,as best shown in Figs. 3 and 4 to remove liquid from the escaping vapor.The eliminator is of more of less conventional construction, comprisinga series of bafiies 52 extending lengthwise of the tube bank in anangular position so that each bafiie overlaps an adjacent one. Theescaping vapor, in passing through these bafiies, throws entrainedliquid against them so that the latter may be caught by the inturnededges 53 of the baffles and drained along the eliminator to thecross-bathe plate 54 from whence it may flow back to the base of theshell for recirculation. The eliminator is required only in that sectionof the shell wherein the velocity of escaping vapor is sufiiciently highto entrain' and carry liquid refrigerant with it. Such is not the casenear the left hand end of the shell and accordingly the plates extendonly from a' point adjacent'the bafile St to some point beyond thecenter'of the tube bank.

The refrigerant vapor is withdrawn from the shell through the outlet 55by a compressor, an absorber, or any other usual device. In theembodiment of the invention illustrated in Figs. 2 to 4 inclusive, thisoutlet is defined by the righthand endof the shell, a flange 56' beingprovided to receive a complemental flange of a compressor or a suitableconnecting conduit. With this arrangernent the I necessity for the usualoutlet opening in the top of the shell, and fora head to cover theright-hand end of the shell, is completely obviated. To do so, however,it is essential that the tube bank shall not extend the full length ofthe shell, and that its right-hand end shall be, blocked off, so tospeak, by the provision of the bafile indicated at 54.

The circulation of liquid refrigerant from the base of the evaporatorshell over the heat exchanging surfaces of the tube bank is achievedprincipally by the percolating action which has been described. It isnot, as'inight be assumed, a mere matter of entraining liquid from-thebase of the shell with the jets of'liquid introduced from the condenser.The energy for lifting, the liquid in the present evaporator is derivedpartly from the change of state of the refrigerant as a result ofheatinterchange. The ability of the jets to entrain liquid is also utilizedbut their principal function is tosupply the intial volume of flash gaswhich. is needed to start the percolating cycle.

Inthe preferred embodiments of the invention like.

' class.

sub-divided at all. The percolating action will still start in thechannels defined by the fins although possibly not so promptly; and itwill continue, through with less complete distribution of liquid attimes.

The principles of the invention are applicable regardless of thecharacter of the refrigerant which is being used. Thus, they may beembodied in evaporators using refrigerants of the high pressure group,such as carbon dioxide, propane, ammonia, freon, and the like, as wellas in others which use low-pressure refrigerants such asdichloro-menthane, trichloro-ethyline and the The main differencebetween these classes of refrigerants, so far as the present inventionis concerned, lies in the fact that with the firstmentioned ones a smallvolume is circulated through the system at a fairly highevaporatorcondenser pressure differential, whereas with the others alarge volume is circulated ata fairly low pressure differential. Theessential dilferences between evaporators designed for theserefrigerants will readily be apparent to those skilled in the art-andwill involve mere changes in the size and section of the tube bank, etc.

The practical evaporator shown in Figs. 3 to 6 inclusive, isparticularly designed for use with a refrigerant of the so-calledlow-pressure class. It is there possibly that the invention has itsgreatest application. Those skilled in the arts will readily appreciatethe impracticability of wetting the heat exchange surfaces bysubmergencein a large volume of a refrigerant of this Surfaceevaporation is needed, and the present invention provides a way tosecure it without requiring an independent pump, and accessories, toshower the bank with refrigerant in the manner now practiced.

Since certain changes may be made in the in-' vention and in thepractical embodiments thereof, it is intended that the foregoing shallbe construed in a descriptive rather than in a limiting sense. I I

What I claim is:

1. A shell and tube refrigerant evaporator comprisinga shell adapted toserve as a path for a volatile refrigerant, a bank of tubes extendingthrough said shell which serve to conduct a medium to be cooled, a poolof liquid refrigerant in the base of said shell which'is insufiicient tosubmerge more than a few rows of tubes at the bottom of the bank,'meansfor supplying additional refrigerant to said pool, at a temperatureabove that prevailing in said pool, and fins extending from said tubesat closely spaced points, which fins and tubes serve to confine vaporousrefrigerant formed in the pool to cause it to create a froth of liquidand vapor, and also to confine said froth so that it may rise throughsaid bank and wet said tubes and fins thereofI 2. A shell and tuberefrigerant evaporator of I the type wherein the tube bank is notsubmerged in liquid refrigerant, such evaporator comprising a shelladapted to serve as a path for a refrigerating fluid, a bank of tubesextending through the shell and serving to conduct a fluid to be vcooled, means defining a plurality 'of channels extending crosswise ofand vertically within the bank of tubes and including the outer surfaces'of the tubes, each such channel having its lower end open adjacent thebase of the shell and its upper end open adjacent the top of the tubebank, and a conduit for discharging liquid refrigerant into the base ofsaid shell whereby flash gasresulting from'the evaporation of some ofthe refrigerant may be confined and caused to lift remaining liquidrefrigerant through said channels and over the outer surfaces of thetubes 'of the bank.

3. A refrigerant evaporator, according to claim 2 further characterizedin that said channels have their open lower ends spaced above the baseof the shell, and in that said conduit is disposed beneath the bank oftubes and is arranged to discharge liquid refrigerant through liquidrefrigerant in the base of the shell beneath the tube bank to carry someof that liquid into the lower ends of said channels.

4. A refrigerant evaporator according to claim 2 further characterizedin that said means includes a plurality of fins extending from thesurfaces of the tubes at closely spaced points.

5. A refrigerant-evaporator according to claim 2 further characterizedin that said tubes extend lengthwise of the shell in a horizontalposition, and in that said means includes a plurality of closely spaced,plate fins extending crosswise of the tubes, and a vertically disposeddividing plate extending crosswise of such fins parallel to the tubes.

8. A refrigerant evaporator according to claim 6 further characterizedby the provision of a substantially vertically disposed plate extendingcrosswise of the fins and dividing the tube bank other section; and bythe provision of means for 6. A shell and tube refrigerant evaporator ofI the type wherein the tube bank is not submerged within liquidrefrigerant in the shell, such evaporator comprising a shell, a bank ofhorizontally disposed tubes extending lengthwise of the shell andpartially filling the same, a plurality of fins extending crosswise ofthe tubes at closely spaced points, means cooperating with the ends ofsuch i fins at the sides of the bank of tubes to define a plurality ofchannels extending vertically within the bank of tubes and having theirloweropen ends adjacent but spaced from the base of the shell and theiropen upper ends .terminating within the bank of tubes, and a conduit fordischarging liquid refrigerant into the base of the shell and fordirecting such liquid within said channels whereby to confine flash gasresulting from the evaporation of some of the liquid to cause it to liftliquid from the base of th shell through the channels over the fins andtubes.

7. A refrigerant evaporator according to claim 6 further characterizedby the provision of a substantially vertically disposed plate extendingcrosswise of the fins and dividing the tube bank longitudinally into aplurality of sections; and in that said conduit is arranged to dischargeliquid refrigerant into the space beneath the open ends of the verticalchannels lying within one section of the bank whereby some of it may belifted by flash gas through such channelsover the fins another section.

returning excess liquid refrigerant from the lastmentioned section tothe space beneath the vertical channel in the firstementioned section.

9. A refrigerant evaporator according to claim 6 further characterizedby the provision of a substantially vertically disposed plate extendingcrosswise of the fins-and dividing the tube bank longitudinally into aplurality of sections; in that said conduit is arranged to dischargeliquid into the base of one section immediately beneath the open lowerends of the vertical channels lying within that section whereby some ofit may be lifted by confined flash gas through such i channels over thesurfaces of the fins and tubes of that section and be discharged intoan,adjacent section; and in that said vertically disposed plate has itslower edge spaced above the base of the shell to provide a passagewayfor the return of liquid from the said adjacent section to thefirst-mentioned one, such passageway being sealed to the passage ofpaper by liquid refrigerant therein.

10. A shell and tube refrigerant evaporator of the type wherein the tubebank is not submerged in liquid refrigerant in the shell, suchevaporator comprising a shell, a bank of horizontally disposed tubesextending lengthwise of the shell and partially filling the same, aplurality of plate fins disposed crosswise of the tubes to define aplurality of channels extending vertically within the bank of tubes,such channels having their lower ends open adjacent but spaced from thebase of the shell and their upper ends open adjacent the top of the bankof tubes, said shell having a reservoir portion in its base beneath thebank of tubes for a small volume of liquid. refrigerant, and a conduithaving a plurality of orifices therein for discharging jets of liquidrefrigerant upwardly into said reservoir portion whereby to entrainliquid from the reservoir and tOgdiTGCt itinto the lower ends of saidchannels.

11. A refrigerant evaporator comprising a shell serving as a path for arefrigerant fluid; a bank I v bank longitudinally into inner and outersections,

said plates cooperating with the fins on the tubes in the inner sectionof the bank to define a plurality of narrow vertical channels; and aconduit extending'along the base of the shell beneath the inner sectionof the tube bank, such conduit having a plurality ofopenings thereinfordischargingliquid refrigerant into the shell and for directing itinto the lower ends of said channels in the inner section.

12. A refrigerant evaporator according to claim 11 further characterizedin that the dividing tube bank whereby liquid refrigerant lifted throughthe channels of the inner section may be discharged into the outersections and flow by gravity over the tubes in such outer sections; andin that such plates have their lower edges spaced above the base of theshell whereby liquid refrigerant collecting in the outer sections mayreturn beneath the edges of such plates to the,

when it reaches predetermined levels in the troughs; and in that thebottom plates are spaced above the base of the shell to providepassageways through which liquid refrigerant escaping from the sidesections may pass back into the inner section.

14. A refrigerant evaporator according to claim 11 further characterizedby the provision of side and bottom plates cooperating with the adjacentdividing plates to form troughs within which the tubes of the two outersections lie, said sideplates having openings therein at points spacedabove their lower edges to permit the overflow of excess refrigerantfrom the troughs, and said bottom plates being spaced above the base ofthe shell to define passageways through which overflowing liquid mayreturn to the inner section, such liquid serving as a liquid sealbetween the center and outer sections.

15. A refrigerant evaporator according to claim 11 further characterizedby the provision of side and bottom plates cooperating with the adjacentdividing plates to form troughs within which the tubes of the two outersections lie, said side plates having openings therein at points spacedabove their lower edges to permit the.

overflow of excess refrigerant from the troughs, and said bottom platesbeing spaced above the base of-the shell to define passageways throughwhich overflowing liquid may return to the inner section, 'such liquidserving as a liquid seal between the inner and outer sections; and inthat plates extend less than the full height of the tion have theirlower edges engaging the base of the shell while the remaining onesterminate short of the base, such extended fins being provided atregularly spaced intervals along the length of the tubes.

16. A refrigerant evaporator according to claim 11 further characterizedby the provision of side and bottom plates cooperating with the adjacentdividing plates to form troughs within which the tubes of the two outersections lie, said side plates having openings therein at points spacedabove their lower edges to permit the overflow of excess refrigerantfrom the troughs, and said bottom plates being spaced 'above the base ofthe shell to define passageways through which overflowing liquid mayreturn to the inner section, such liquid serving as a liquid seal besomeof the fins for the tubes of the inner sectween the inner and outersections; in that some of the fins for the tubes of theinner sectionhave their lower edges engaging the base of the shell while theremaining ones terminate short of the base, such extended fins beingprovided at regularly'spaced intervals along the length of the tubes;and in that said conduit has at least one opening discharging liquidrefrigerant into the base of the shell between each adjacent pair ofextended fins.

17. A refrigerant evaporator according to claim 11 further characterizedby the provision of a cap at one end of the shell; fluid supply anddischarge connections between such cap and the tubes; a bafile extendingcrosswise of the shell adjacent the end of the tube bank, which isremote from said cap; and in that the other end of the shell is adaptedto serve as an outlet for the discharge of refrigerant from the shell.

18. A refrigerant evaporator comprising a horizontally disposed shellserving as'a path for a refrigerant fluid; a bank of tubes extendinglengthwise of and partially filling said shell, such tubes beinginterconnected at their opposite ends and serving to conduct a fluid tobe cooled; a cap on one end of the shell; fluid supply and dischargeconnections between such cap and said tubes; a baffle extendingcrosswise of the shell at that end of the tube bank which is remote fromsaid cap; a conduit for supplying refrigerant to the base of the shell;and an opening in the shell for the discharge of refrigerant vaportherefrom, such opening comprising the other end of the shell.

ROBERT W. WATERFILL.

CERTIFICATE OF CORRECTION. Patent N00 2,2LL7,107, 7 June 21;, 19th.,

[ROBERT w. WATERFILL.

It is hereby certified thet error appears in the printed specificationof theabove I number-ed patent requiring correction a s follows: Page14,. sec.. ond column, line 1, for "longi'tddinal" read --longitudina1-;page 5, "sec-- 0nd column, line 55, claim 9, for "paper" read -vapor--;and that the said Letters Patent should be read with this correctiontherein that the Same may conform to the record of the case in thePatent Office; Signed and sealed this 2nd day of September, A. D.1914.1,

Henry Va'n .Arsda le, (Seal) Acting Commissioner of Patents"

